Reaction entropies, ΔS°rc, have been determined for a series of transition-metal ions electrostatically bound into Nafion films. Complexes with hydrophobic, "shielding" ligands such as Ru(2,2′-bipyridine)3 3+/2+ and Co(2,2′-bipyridine)3 3+/2+ yield similar ΔS°rc values in Nafion films and in aqueous solution, indicating that the electrochemically active probes reside in a predominantly waterlike local environment in the polymer film. Complexes containing aquo and ammine ligands yield markedly lower ΔS°rc values in Nafion than in aqueous media (μ = 0.1 M). The ΔS°rc values for these Nafion-bound systems are similar to values measured for the Ru(NH3)6 3+/2+ system in concentrated aqueous salt solutions (5 M LiCl). The ΔS°rc measurements imply that the outer-sphere electron-transfer work terms for polymer bound ions may be lower than those observed in typical aqueous solutions. Differential free energies, enthalpies, and entropies of transfer for the redox reaction M(III) + e- → M(II) from aqueous media to Nafion have also been determined.
|Number of pages||2|
|Journal||Journal of Physical Chemistry|
|Publication status||Published - 1986|
ASJC Scopus subject areas
- Physical and Theoretical Chemistry